. and two weeks ago, he traveled to benghazi to review plans to establish a new cultural center and modernize a hospital. that's when america's compound came under attack. >> that's the first we learned about exactly what stevens was doing in benghazi, a city the u.s. had been warned was not safe. and the president continued in his speech vowing to find the killers. >> the attacks on the civilians in benghazi were attacks on american. we are grateful for the assistance we received from the libyan government, and from the libyan people. there should be no doubt that we will be relentless in tracking down the killers and bringing them to justice. >> relentless in tracking down the killers, and bringing them to justice. it's a promise. but does that promise add up? it has been 14 days since the american ambassador to libya and three other americans were killed. and we still don't know why, and we still don't know who did it. and what we do know, from our reporting here at cnn, is this. in terms of a warning, three days before stevens was killed, the libyan military told senior u.s.